This invention relates to electrical string musical instruments and the like, and more particularly to electromagnetic pickup devices for use with such electrical string musical instruments.
Electromagnetic pickup devices are used in conjunction with string musical instruments such as electric guitars to convert the vibrations resulting from the movement or "picking" of the strings into electrical signals, for subsequent transmission to amplification means to produce a desired sound effect. One type of electromagnetic pickup device employed in electrical string musical instruments such as electric guitars is a single-coil pickup, such as disclosed in U.S. Pat. No. 2,968,204 (Fender), in which a single coil portion has a plurality of magnetic pole pieces, with each pole piece operatively associated with a string of the instrument, the pole pieces lying in a plane spaced from the common plane of the strings, with each string disposed in a plane extending through a space between two adjacent ones of the pole pieces, so that a given string in its "at rest" position is located above and between two adjacent pole pieces.
Another arrangement of an electromagnetic pickup device relative to the strings of an electrical musical instrument is disclosed in U.S. Pat. No. 3,177,283 (Fender), in which an electric guitar having a first electromagnetic pickup operatively associated with certain wound strings of the guitar, and a second electromagnetic pickup adjacent to the first pickup, wherein the second pickup is operatively associated with the unwound strings of the guitar.
Yet another type of electromagnetic pickup device employed in electrical string musical instruments such as electric guitars is a dual-coil or "humbucking" type pickup, which generally has first and second coil portions each having a plurality of spaced-apart magnetic pole pieces operatively associated with the strings of the instrument. In a typical "humbucking" pickup, the pole pieces of the coil portions are positioned relative to one another such that a given string of the instrument in its "at rest" position lies directly above a corresponding pair of pole pieces of the first and second coil portions, which are operatively associated with the string.
The signal transmitted by an electromagnetic pickup device employed in conjunction with a string musical instrument is strongly dependent upon the motions of each guitar string in the immediate vicinity of each string's corresponding magnetic pole pieces. As is well known to those skilled in the art, the strength of the magnetic field in the vicinity of a magnetic pole piece diminishes with the square of the distance from the pole piece. Thus, the signal transduction of the pickup for a given string similarly diminishes, i.e. the area of a given vibrating string susceptible to signal transduction is only that area very close to the face or faces of the corresponding pole piece or pieces.
It is also well known to those skilled in the art that the complex transverse motions of a vibrating string of a string musical instrument, which are converted to an electrical signal or "picked up" by an electromagnetic pickup device, may be precisely described as the algebraic sum of the vibrating string's fundamental vibrational wavelength and its many harmonic wavelengths. The particular tonal quality or timbre of any musical sound produced by the instrument is strictly dependent upon the relative intensities of the corresponding fundamental and harmonic frequencies.
As previously described, in the case of a typical "humbucking" pickup operatively associated with the strings of an electric guitar, the pickup has first and second coil portions each having a plurality of spaced-apart magnetic pole pieces, wherein the pole pieces are positioned relative to one another such that each string in its "at rest" position lies directly above its corresponding pole pieces of the first and second coil portions. In a perfect guitar string of infinite length, vibrating only at its fundamental frequency, the excursion of the guitar string across the face of each of the two pole pieces per string would be precisely simultaneous and exactly perpendicular to the long axis of the guitar string. The signals picked up from the section of guitar string in the immediate vicinity of each of the two corresponding pole pieces per string would be precisely identical, and by the inversion of electrical and magnetic phase in the two adjacent halves of the pickup, the two signals would mix in phase and perfectly reinforce each other to give an output signal of exactly twice the intensity of either individual signal.
However, in actual practice, each string has a finite length and vibrates at its fundamental plus many harmonic frequencies. During typical playing of the instrument, the freely vibrating length of a guitar string is on the order of only about 12 inches, and the wavelengths of the string's vibrational harmonics are corresponding fractions of this short length. At any given instant in time, it may happen that one harmonic component of a vibrating guitar string has a wavelength of exactly twice the spatial separation of the two pole pieces per string. With the typical guitar string and typical "humbucking" pickup previously described, this would occur around the seventh and eighth harmonics of the fundamental frequency. When this occurs, the guitar string excursion representing these harmonic components of string vibration in the immediate vicinity of each pole piece per string would be of approximately equal length but in opposite directions. By the inversion of electrical and magnetic phase in the two adjacent halves of the pickup, the signals of these wavelengths are effectively cancelled. Other harmonics are similarly cancelled to a lesser extent, and still other harmonics are reinforced by the same means. This alteration of the final mix of fundamental frequency plus harmonics results in a particular timbre or tonal quality that may be perceived by the listener as unnatural.
It is well-known among persons skilled in the art of guitar playing that the tonal quality of a typical "humbucking" pickup as previously described is distinctly different from that of a single-coil pickup (in which only one magnetic pole piece is associated with each string) and that the single-coil timbre is superior and more pleasing in many styles of playing. It is theorized that the reasons for the inferiority of timbre in the typical "humbucking" guitar pickup is the unnatural reinforcement and cancellation of certain harmonic frequencies by the mechanism already described. However, in certain types of music playing, such as so-called "hard rock" music, a "humbucking" pickup is preferred by those skilled in the art. In view of the foregoing, it would clearly be advantageous to have a dual coil or "humbucking" pickup device which is less susceptible to the unnatural reinforcement and cancellation of certain harmonic frequencies, as previously described.
The electromagnetic pickup device of this invention provides such a dual coil pickup without the above-described attendant problems. It is one object of this invention to provide an electromagnetic dual coil pickup device for use in an electrical string instrument, comprising a first coil portion having an upper surface and carrying a plurality of spaced apart magnetic pole pieces, a second coil portion having an upper surface and carrying a like plurality of spaced apart magnetic pole pieces, each of the strings being operatively associated with a pair of pole pieces, one of the pair on each of the coil portions, each of the strings having a resting position and the central vertical axes of the pair of magnetic pole pieces associated with at least one string lying in a plane which intersects the string. It is a feature of this invention that when the above-described pickup device is operatively associated with the strings of an electrical string musical instrument, a higher quality and enhanced sound effect with a more natural and more pleasing timbre or tonal quality is advantageously produced from the instrument.
It is another object of this invention to provide an electrical string musical instrument comprising the above-described electromagnetic pickup device of this invention. It is a feature of the electrical musical instrument of this invention that all of the strings of the instrument are operatively associated with the pickup device in such a manner that, when caused to vibrate or "picked", the vibrating strings advantageously produce a higher quality sound effect with a more natural and more pleasing timbre or tonal quality than that typically produced by an electrical string musical instrument employing a conventional dual coil pickup device.